Electronic systems with safety-critical requirements must be projected following the fail-safe equipment philosophy. Therefore, all operational states and all failure states must be known and analyzed. If one of these failure states has been reached, prompt action must be taken to leave it, preventing great material losses, or risk to the people or the environment.
Monoprocessed computer architecture is presented for use in safety-critical applications, such as train control systems. The main advantages in using this kind of architecture are its higher reliability and safety and lower cost, when compared to other architectures, such as duplicated architectures with a comparator, or triplicated architectures with a voter.
The proposed monoprocessed architecture is composed by a main processor and a watchdog processor. The watchdog processor has the function of monitoring the main processor behavior. The watchdog processor is much simpler than the main processor. The main processor software is designed using special coding techniques. The basic technique is the software replication that consists of two or more different implementations of the same program specification. These software versions should produce the same results and are executed sequentially in the same processor.
The target of this proposed architecture is to increase the system fault coverage factor. This factor is responsible for the detection of any fault that may be dangerous to the system, enabling the prevention of such condition.